It may take 40 years for the site to appear like "a normal reactor at the end of its life."

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A schematic of the Fukushima nuclear power plant hints at the complexity of decontamination and decommissioning operations.

TEPCO

The Governor of Fukushima Prefecture (left) visiting 1F last year.

TEPCO

Seven years on from the Great East Japan Earthquake of March 2011, Fukushima Daiichi nuclear power plant has come a long way from the state it was reduced to. Once front and center in the global media as a catastrophe on par with Chernobyl, the plant stands today as the site of one of the world’s most complex and expensive engineering projects.

Beyond the earthquake itself, a well understood series of events and external factors contributed to the meltdown of three of Fukushima’s six reactors, an incident that has been characterized by nuclear authorities as the world’s second worst nuclear power accident only after Chernobyl. It’s a label that warrants context, given the scale, complexity, and expense of the decontamination and decommissioning of the plant.

How does a plant and its engineers move on from such devastation? The recovery initiatives have faced major challenges, constantly being confronted by issues involving radioactive contamination of everything from dust to groundwater. And those smaller issues ultimately complicate the remediation effort's long-term goal: to locate and remove the nuclear fuel that was in the reactors.

A sense of scale

Jonathan Cobb, spokesperson for the World Nuclear Association, spoke with Ars about the scale of Fukushima, explaining that radioactive releases in Japan were much smaller than at Chernobyl, and the accident resulted in no loss of life from radiation: “Of course, this doesn’t take away from the enormous task currently being faced at Fukushima.”

The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported in May 2013 that radiation exposure following the Fukushima accident didn’t cause any immediate health effects and that future health effects attributable to the accident among either the general public or the vast majority of workers are unlikely. A 2017 paper from UNSCEAR reports that these conclusions remain valid in light of continued research since the incident.

Even the most at-risk citizens, those living in Fukushima prefecture, are only expected to be exposed to around 10mSv as a result of the accident over their lifetimes. “For reference, the global average natural background radiation tends to be around 2.4mSv/year, but even 20mSv/year isn’t exceptional,” said Cobb.

Still, the accident was rated a 7 on the International Nuclear and Radiological Event Scale (INES), which is the highest rating possible, and designates it a Major Accident due to high radioactive releases. Estimates vary slightly, but Japan's Nuclear Safety Commission report puts total releases at 570 petabecquerels (PBq) iodine-131 equivalent. (For comparison, Chernobyl released 5,200PBq iodine-131 equivalent.)

But the severity of the accident is probably most keenly felt in the scale of the cleanup. The incident has necessitated the ongoing cleanup and decommissioning of the plant—something that Tokyo Electric Power Company (TEPCO), the plant’s owner and operator, is responsible for. Even though the plant is seven years into the cleanup and has accomplished a great deal, we won’t see a conclusion for decades yet.

Damage to reactor Units 1-4 in the aftermath of the March 2011 earthquake.

TEPCO

In addition to damage to infrastructure and buildings, a large amount of wreckage was left strewn around the plant complex.

TEPCO

Remotely operated machines were involved in clean-up of the most contaminated areas.

TEPCO

A look inside the Primary Containment Vessel (PCV) of Unit 2.

TEPCO

A composite image of photographs taken inside the Primary Containment Vessel (PCV) of Unit 2.

TEPCO

A look at debris in the spent fuel pool of Unit 3.

TEPCO

Meltdowns and immediate priorities

Remarkably, seismic shocks of the magnitude 9 earthquake didn’t cause any significant damage to the earthquake-proofed reactors; rather, the tsunami knocked out power that precipitated reactor meltdowns in Units 1, 2, and 3. Subsequent explosions caused by hydrogen buildup (from zirconium cladding of fuel assemblies melting and oxidizing) in Units 1, 3, and 4 then expelled radioactive contamination, most of which fell within the confines of the plant.

Cobb explained that in the aftermath of this, the ongoing risk posed by radionuclides (notably, iodine-131 and cesium isotopes 134 and 137) depended on their half-lives. Iodine-131, with a half-life of just eight days, posed virtually no threat at all after just several months. It has been cesium-134, with a two-year half-life, and cesium-137, with a 30-year half-life, that have been the major focus of decontamination efforts. “Radioactive decay means that we’ve seen a reduction in contamination simply through time passing; at the plant, however, my expectation is that the majority of reduction has been due to efforts of TEPCO. Conditions have improved markedly and a sense of normalcy has returned.”

It’s useful to take stock of what TEPCO had to contend with from the outset. Lake Barrett, a veteran of the US nuclear energy industry who spent several years at the helm of decommissioning work at Three Mile Island reactor 2, is currently an independent special advisor to the Japanese Government and TEPCO board of directors. He told Ars, “When everything goes to hell on you, you go back to basics. You’re concerned with accident response and immediate recovery of the situation. Over the longer timeframe, the decontamination & decommissioning (D&D) focus shifts to a more deliberate approach to major technical challenges.”

Barrett explained that reactor stabilization at Fukushima—an imperative of the immediate recovery—has long since been achieved. Temperatures within the Reactor Pressure Vessels (RPVs) and Primary Containment Vessels (PCVs) of Units 1-3 are stable at between 15 to 30ºC, and there have been no significant changes in airborne radioactive materials released from reactor buildings. This qualifies as a ‘comprehensive cold shutdown’ condition.

Barrett explained how the issue of cooling is mostly non-existent at this point: “The three melted reactor cores emit less heat than a small car. Decay heat was a huge issue in the first weeks, but it’s no longer an issue. And while TEPCO still injects water onto the cores, this is more for dust suppression than anything else.”

With the reactors stable, early phases of TEPCO’s work simply involved debris clearing and restorative efforts throughout buildings and across the 3.5 square miles of the plant—both having been ravaged by the earthquake and tsunami. In the most contaminated places, remotely operated machines undertook most of the work. To reduce environmental contamination, they also removed top soils and vegetation, deforested the site, and then applied a polymer resin and concrete across much of the plant complex. This has locked contaminated material in place and limited the flow of groundwater through the site.

Other work has been more substantial. Units 1, 3 and 4 were blown apart and have had to be reinforced and encased, both for safety and to prevent spread of radioactive material. Although Unit 2 retained its roof, TEPCO decided to dismantle the upper building nonetheless, as it will facilitate removal of fuel from the reactor.

At the peak of these operations, some 7,450 persons worked at Fukushima. As operations have evolved, the workforce has declined to a not inconsiderable 5,000 daily personnel. With such levels of permanent staffing, it’s little wonder that a new rest-house, cafeteria, shops, and office building have all been built.

The efforts have, in a practical sense, meant that the majority of the site has transitioned to a stable, relatively risk-free environment. Describing the decommissioning as an “enormous challenge never before undertaken by humanity,” Seto Kohta of TEPCO told Ars: “We have overcome the state of chaos that ensued after the accident and have succeeded in reducing site dose levels to an average of less than 5μSv/h, with the exception of the vicinity of Units 1-4.” (Global background levels are <0.5µSv/h.)

TEPCO reports that the additional effective dose (i.e. additional to natural background radiation) at the plant’s boundary has declined to the target value of less than 1mSv/y.

This is not to say the plant is without signs of past problems—far from it. Felled trees sit waiting for incineration; huge mounds of soil lie under tarps; buildings retain marks of past trauma; and with environmental dosage a perennial concern, close to a hundred dose-rate monitors are positioned around the site.

Kohta also noted that while “95 percent of the site no longer requires the donning of full- or half-face masks or coveralls,” some level of protection is still required for working around the plant according to three levels of contamination. The vast majority of the plant grounds are in what’s termed Zone G, which requires just generic coveralls and disposable medical masks. Zone Y provides a perimeter around the Units 1-4 and necessitates heavier-duty coveralls and either full- or half-face masks. And lastly there is Zone R, closer to and including the reactor buildings, requiring double-layered coveralls and full-face masks.

I feel like this is something that is overlooked about the entire situation. The tsunami and TEPCOs arrogance/fear lead to this becoming such a massive failure. My belief is that expanding our nuclear capability is the way forward as we continue to improve our renewable and storage options, just don't think politicians are willing to take the flak to make it happen.

The knowledge gathered and new technologies devised to deal with the contamination and cleanup will be useful for any future incidents. Additionally, engineers will learn how to better design these power plants to be more resilient to natural or man-made disasters.

40 years is a shorter time frame for decommissioning than I expected.

Units 1-3 at Fukushima Daiichi will need to remain entombed indefinitely despite the overall site being decommissioned?

I'm confused why they haven't just flooded the site. While I don't generally encourage littering, it would stop all the radioactive dust concerns, and be a lot cheaper than decontamination. They also are already at the point where you're fine living even right next to the plant. This wasn't Chernobyl. It's probably just a good lesson in the public fear of radiation which is altogether over the top, along with regulatory agency requirements. Of course the small dataset of people with prolonged low level radiation exposure is limiting but it seems that low level radiation isn't very dangerous at all, and in fact probably harmless.

I'd think because it's a temporary containment, not a permanent one. Case in point: the "freeze wall" in place will only last so long as there's power to the refrigeration units. Another earthquake could easily disrupt it's functioning (not to mention crack what containment vessels are there now).

"That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”"

Chernobyl notwitstanding, Nuclear is actually the safest form of power we have ever devised. We will continue to make it safer.

As for costs, we need to look at this more like an insurance risk pool. Like homeowners insurance. Your house *might* burn down, and cost the insurance pool $350k. But, you only pay maybe a few hundred or a thousand per year for insurance, because that risk is spread across a large number of homes, most of which aren't going to burn down.

Nuclear power accidents are the same way: Fukushima was like rolling a '1' on a D20 about 4 times in a row. Highly unlikely, and yet it did happen, because in life, sometimes highly unlikely things just happen:

* Japan just happened to be hit with a once-in-thousand-year mega earthquake and monster tsunami during the lifetime of that particular nuclear reactor, and that happened to be within 60 years of the discovery and advent of this completely-new-to-mankind type of power. Yes, TEPCO and others also didn't take the threat seriously enough, and didn't plan for it. But, it's also super bad luck that it just happened to happen within such a short time (in terms of history) of the construction of that plant.

* We keep developing newer nuclear plant designs that are safer than previous designs, and will continue to do so throughout human history. Again, it's bad luck that the once in a thousand year tsunami/eq hit during the early part of that learning curve, when the plant designs are the most vulnerable to such events.

But, EVEN SO, the consequences of this reactor meltdown are actually pretty spectacularly small. Keep in mind that fire, man's first energy source, has been responsible for burning down large sections of cities, killing thousands, repeatedly throughout history.

Nuclear power is and still should continue to be an option, because it's a rich, controllable power source that can provide mankind with power for billions of years, with very small, manageable environmental consequences.

I don't, personally, view Fukushima as a 'disaster'. It was a reactor casualty, but that has caused very little actual real harm.

"That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”"

How else would you measure it? Literally half decays away in time x. The "full life" for all radioisotopes is essentially infinite.

As a practical matter though ten half lifes mean 1 - 0.5^10 = 99.902% has decayed away. At some point it has decayed to a level that is no longer a material concern how long that is depends on the starting amount and the half life.

It's a convenient aggregation. It's not really possible to predict when an individual particle might decay, it might be in one minute, it might be in years. But as a group, you know when roughly half of the original given amount would be decayed.

Kind of like how you can't know for certain if a coin flip is a head or tails, but you can be confident you would need to flip 1 million coins to get 500K heads.

"That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”"

Chernobyl notwitstanding, Nuclear is actually the safest form of power we have ever devised. We will continue to make it safer.

As for costs, we need to look at this more like an insurance risk pool. Like homeowners insurance. Your house *might* burn down, and cost the insurance pool $350k. But, you only pay maybe a few hundred or a thousand per year for insurance, because that risk is spread across a large number of homes, most of which aren't going to burn down.

Nuclear power accidents are the same way: Fukushima was like rolling a '1' on a D20 about 4 times in a row. Highly unlikely, and yet it did happen, because in life, sometimes highly unlikely things just happen:

* Japan just happened to be hit with a once-in-thousand-year mega earthquake and monster tsunami during the lifetime of that particular nuclear reactor, and that happened to be within 60 years of the discovery and advent of this completely-new-to-mankind type of power. Yes, TEPCO and others also didn't take the threat seriously enough, and didn't plan for it. But, it's also super bad luck that it just happened to happen within such a short time (in terms of history) of the construction of that plant.

* We keep developing newer nuclear plant designs that are safer than previous designs, and will continue to do so throughout human history. Again, it's bad luck that the once in a thousand year tsunami/eq hit during the early part of that learning curve, when the plant designs are the most vulnerable to such events.

But, EVEN SO, the consequences of this reactor meltdown are actually pretty spectacularly small. Keep in mind that fire, man's first energy source, has been responsible for burning down large sections of cities, killing thousands, repeatedly throughout history.

Nuclear power is and still should continue to be an option, because it's a rich, controllable power source that can provide mankind with power for billions of years, with very small, manageable environmental consequences.

I don't, personally, view Fukushima as a 'disaster'. It was a reactor casualty, but that has caused very little actual real harm.

That said, it did cause real financial harm to TEPCO. And compared to other low carbon energy sources, only hydroelectric via dams has the same potential for "catastrophic" failure. The catastrophic failure modes for wind/solar are much less dramatic.

tritium has a half life of a dozen years, so physics won’t clean up the water for us.

Physics absolutely will clean up the water from tritium contamination. Are there other policies that mandate cleanup before a certain time? The half life for tritium really isn't that long.

I think he means physics (nuclear decay) won't solve this in any reasonable amount of time. The half life of tritium is reasonably short but they have a thousand fucktons of highly concentrated (Bq/L) tritiated water. That is metric fucktons of course.

Diluting it in a measured release is probably the least bad option. Keeping it in tanks for a century or two isn't really viable and runs the risk of a tank failure leading to a concentrated release which would be far worse. The low biological half life (how long it stays inside you) of tritium means it is really only harmful if something living consumes a lot of it.

Of course to those who don't understand nuclear physics a measured release sounds like the end of life as we know it so I expect a ton of political pushback and fear mongering (a nuclear death plume headed for California) even if it is the most sensible option.

"That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”"

tritium has a half life of a dozen years, so physics won’t clean up the water for us.

Physics absolutely will clean up the water from tritium contamination. Are there other policies that mandate cleanup before a certain time? The half life for tritium really isn't that long.

I think he means physics (nuclear decay) won't solve this in any reasonable amount of time. The half life of tritium is reasonably short but they have a thousand colossal fucktons of tritiated water.

That's the beauty of half-life though. It doesn't matter the quantity, after about 7 half-lives it's essentially gone. That's less than 90 years in this case which we could easily store safely for that period of time. But if the time frames they have to solve this in are much shorter even just two half lives would make dilution easier.

hm, japan has stepped up and is cleaning up... BUT, in the US who is cleaning up Rochesters toxic dump caused by Kodak?.... (too expensive they say.. so if japan can clean up... why can the US not clean up the toxic yet not radioactive mess that Kodak left behind, and IMO will never be cleaned up because of Kodak’s insolvency...

tritium has a half life of a dozen years, so physics won’t clean up the water for us.

Physics absolutely will clean up the water from tritium contamination. Are there other policies that mandate cleanup before a certain time? The half life for tritium really isn't that long.

Depending on how concentrated it is, cleaning the tritium water could potentially pay for itself. The stuff is seriously expensive. The most recent number I could find is from 2000; but it put the price at $30k/gram.

It could presumably be separated out using the same process used to separate deuterium heavy water from the normal sort.

Living in eastern Washington state, there’s always Hanford... Don’t have any idea when that’ll get done. Maybe in 100 years or so. Contaminated groundwater will get to the Columbia River. sigh

Point being, Hanford was picked as a test site specifically because no one was living anywhere for a radius of a hundred miles or so. There’s no one to speak for Hanford; there’s much more pressure to fix Fukushima Daiichi.

Fukushima was a case where, generally, we did everything right, but everything that could go wrong went wrong. That is why the overall effort on containment, control, and mitigation is seen by many as "easy" (in the relative sense of cleaning a major nuclear disaster). I'm not saying this was not a problem, but it could have been far worse had we not had response procedures in place.

Compare what happened here to what happened at Chernobyl, where nothing was done right and everything that could go wrong did, and it helps put things into perspective. Seriously, read up on it! It is absolutely fascinating. Wikipedia has the precise timeline of events leading up to and after meltdown, including communication logs and emergency responses, and there are a ton more articles on the ongoing efforts on containing the slagged material.

hm, japan has stepped up and is cleaning up... BUT, in the US who is cleaning up Rochesters toxic dump caused by Kodak?.... (too expensive they say.. so if japan can clean up... why can the US not clean up the toxic yet not radioactive mess that Kodak left behind, and IMO will never be cleaned up because of Kodak’s insolvency...

am i wrong in thinking that the 2091 pink filters on those guys filtration masks aren't really suited for nuclear waste cleanup? I mean... that's a great filter for mold, but... i'd want something that would keep radioactive particulate from entering into my lungs/body.

The worst part about longer-term radioactivity is not necessarily the gamma radiation (which is known for being more penetrating than Quagmire from Family Guy), but the Alpha and Beta particles. It doesn't take much to stop them, so yes, even a simple painter's mask could very well be efficient at protecting your lungs. In the industrial world, this is known as "Level C" protection. Essentially, just be covered from head to toe with glasses and a mask with decent filtration, and yes, you would be adequately protected. You wouldn't need a full SCBA (self-contained breathing apparatus) with the X-Files 'bubble suit' to protect from mere Alpha/Beta radiation.

(spend nearly the last decade of my USAF career as a WMD tech, with a focus on radiation)

am i wrong in thinking that the 2091 pink filters on those guys filtration masks aren't really suited for nuclear waste cleanup? I mean... that's a great filter for mold, but... i'd want something that would keep radioactive particulate from entering into my lungs/body.

Everything's fine, no loss of lives, engineering will solve all problems, so let's go on like before, period. All hail progress!

15k people died because of the 2011 Tohoku earthquake and tsunami. 4 people died because the Fujinuma Dam collapsed. No one died at Fukushima so far.

Yes, this site will be a mess for decades to come.Go look at an open pit coal mine to see if its much better.

Or what went through my mind was, okay, death toll from this nuclear accident was zero, or that's what they think for now -- I wouldn't be surprised if some people exposed very early on at the plant didn't end up with elevated cancer rates, but still the death toll will be quite low.

How many have died in the last 50 years in coal mines? How many in mines of any sort, since all renewable forms of energy use extracted raw materials? How many die from pollution relating to traditional energy production? How much is the quality of life reduced, relative to clean power, from traditional power generation?

I suspect more people died in mines just in China just last year, if the true numbers were reported, than have died in all nuclear energy accidents in history, both direct and indirect, long-term cancer deaths.

I think it's instructive to think about how many more people would be alive, and how much less pollution would be in the atmosphere, if the eco-warriors hadn't succeeded in strangling the industry in the West with cost-exploding red-tape and outright opposition decades ago, and if we'd all instead ended up with French-like, 80+% of grid power coming from nuclear.

And I didn't even mention global warming -- how many tons of CO2 wouldn't of been put in to the atmosphere?

It was a huge missed opportunity. I think nuclear, reasonably regulated, still has a place in a world where renewable power is falling in cost but grid storage still isn't cheap enough, but in general it's politically untenable.

EDIT: And also, consider the huge implications of a world where natural gas (from Russia) wasn't critical for keeping Europe warm through the winter, and where the West thereby had significantly reduced fossil fuel needs from Russia and the Middle East in general, what with their domestic reserves freed up by nuclear to focus on transportation needs.

tritium has a half life of a dozen years, so physics won’t clean up the water for us.

Physics absolutely will clean up the water from tritium contamination. Are there other policies that mandate cleanup before a certain time? The half life for tritium really isn't that long.

I think he means physics (nuclear decay) won't solve this in any reasonable amount of time. The half life of tritium is reasonably short but they have a thousand fucktons of tritiated water (metric fucktons of course).

Diluting it in a measured release is probably the least bad option. Keeping it in tanks for a couple centuries isn't really viable and runs the risk of a tank failure leading to a concentrated release. Of course to those who don't understand nuclear physics a measured release sounds like the end of life as we know it so I expect a ton of political pushback and fear mongering (a nuclear plume headed to California) on a measured release even if it is the most sensible option.

I agree re: measured release. People flip out, but if done properly, it's literally a drop in the ocean compared to all the NORM (naturally occurring radioactive materials) that are in the ocean. Our environment naturally produces tritium from interactions between cosmic rays and atmospheric nitrogen. Cosmic rays are constantly 'shining' on our atmosphere, and while the amount of tritium produced, when diluted in the ocean and groundwater, end up with extremely minute quantities, if you multiplied the amount per liter by the number of liters in all the worlds oceans, rivers, lakes, etc, you come up with a number much much larger than the amount of tritium in the Fukushima tanks.

If you dillute out the tritium from Fukushima into the entire pacific ocean, indian ocean, and eventually all the other worlds oceans as the waters mix, it wouldn't be a measurable change in the overall concentration of tritium in water.

Those who are anti-nuclear might conclude that if you are doing that routinely for nuclear plants, eventually it will accumulate, but, again, the vast majority of nuclear plants in the world don't routinely create large amounts of tritium (though they do produce some from their cooling water), so it's not going to add up to enough tritium to be an issue, ever.

Environmentalists sometimes say they following phrase, snidely, but in some cases it's actually true: The solution to pollution is (sometimes) dilution.

I have little to add other than to say this was an excellent, informative article.

Agreed. And to add that the Japanese, however unfortunate from this accident, are an amazing people. I hope some (cough) other coastal plant locations at a larger (cough) country are watching and learning.

I think anytime there are articles that talk about radiation, there should be a lot of context included, since the layman hears "radiation", they think "nuclear bomb", "The Hulk", or something about growing a 3rd arm. This article does include some context, which is welcome, but I think a nice colorful chart helps also. Thankfully, XKCD did the deed many years ago, and it is quite informative (found at https://xkcd.com/radiation/):

hm, japan has stepped up and is cleaning up... BUT, in the US who is cleaning up Rochesters toxic dump caused by Kodak?.... (too expensive they say.. so if japan can clean up... why can the US not clean up the toxic yet not radioactive mess that Kodak left behind, and IMO will never be cleaned up because of Kodak’s insolvency...

To be fair, that could be worse. Anti-nuke activists like to talk about how many thousands of years radioactive waste can pose a hazard, but how long do pollutants like lead, cadmium, and mercury persist?

am i wrong in thinking that the 2091 pink filters on those guys filtration masks aren't really suited for nuclear waste cleanup? I mean... that's a great filter for mold, but... i'd want something that would keep radioactive particulate from entering into my lungs/body.

I honestly wasn't sure, it's why i asked the question. Personally, even if it's over kill i'd chose to spend $15+ on the filters that block everything vs the $6.81 kmart special... I *know* they're still good filter despite the price, i just didn't realize that they were good at this type of work as well. i mean, great work 3M, that's money *VERY* well spent. The 2091's will be my goto P100's from now on.